Torbutton

Torbutton is the component in Tor
Browser that takes care of application-level
security and privacy concerns in Firefox. To keep you safe,
Torbutton disables many types of active content.

Now that the Tor Browser
includes a patched version of Firefox, and because we don't
have enough developer resources to keep up with the accelerated
Firefox release schedule, the toggle model of Torbutton is no
longer supported. Users should be using Tor Browser,
not installing Torbutton themselves.